Category Archives: Rock pooling tips

Nights out tend to become a distant memory when you’re a parent. For the most part I don’t miss them. I have, however, been looking forward to Junior being old enough to join me for night time rock pooling. Towards the end of last year, we tried it for the first time and, although the conditions weren’t ideal, he’s been asking to go again ever since.

The best low tides always happen around the middle of the day, and the middle of the night, but we compromise for this first family expedition of the year, choosing a reasonable low tide at around 10.30pm. The warm, calm weather provides good opportunities for seeing nocturnal activity and tonight I’m trying out my ultraviolet (UV) torch.

It doesn’t disappoint.

Head torch at the ready – night time rock pooling is a perfect adventure

I’ve always known that certain species glow under UV light, but I had no idea how much. We’ve barely taken ten paces out across the rocks when we see our first snakelocks anemone, shining from the darkness like an eerie green beacon. The colour is wonderfully alien.

Snakelocks anemone at night under UV light – a true alien of the Cornish rock pools

This fluorescence is caused by certain proteins within the animals that take in light of one colour and emit it as another. Some deeper water species can use these properties to appear red, even though red light is filtered out as it passes through the water, meaning the only light available to underwater creatures is UV or blue.

It’s not clear why snakelocks anemones and other sea creatures might want to fluoresce in this way. It seems there may be some benefit in it for their symbiotic algae or it might give them sun protection. It may just be a by-product of a protein that’s useful in other ways. Whatever the reasons, it produces an incredible glow. Junior is already talking of coming back at Halloween.

A spooky night-time rock pooling walk is definitely on the programme for this Halloweeen!

It’s not just the anemones that take our breath away. If you’re used to rock pooling in daylight when most animals are hiding away under rocks and seaweed, the sheer level of activity in after dark takes you by surprise.

A scratching, crackling sound stops us in our tracks. It’s coming from the rocks. I lift the seaweed to show Junior a group of limpets. Some are feeding, their strong radulas scouring seaweed off the rock and chipping bits of rock. Others are setting into their home scars, grinding their shells into their grooves to create a perfect fit. Close-up, their activities make a surprising amount of noise.

Limpets on their way home as the tide retreats

Most rockpool animals are largely nocturnal. Pools that seem empty in daytime become bustling cities of activity. We watch hermit crabs milling around in large numbers, crabs marauding through the pool and across the rocks, fish floating in plain sight. Prawns come towards the light and watch us before shooting away backwards.

A green shore crab looking blue in the UV lightHermit crabs are more active at night, every pool is teeming with them

Other Half spots a small species of spider crab (Macropodia sp.) decorated with long fronds of seaweed edging sideways across the pool. It’s moving too fast to take a clear photo in the poor light. The blurring makes it look even more alien.

A blurry small spider crab (Macropodia sp) moving across sand.

A scorpion fish lies still on the sand, watching out for prey.

A scorpion fish (Taurus bubalis) hiding in plain sight.

One surprise is the stunning colours of the seaweeds under the UV light. Some of the dark red seaweeds take on a far more intense, bright colour, glowing red, pink and orange. Where the top shells have worn spires, their tips glow pink.

A grey topshell on a red seaweed under UV light

After an hour, tiredness and cold begin to set in. We switch off our torches and take a moment to gaze at the stars before we head home to bed. Junior is already asking if we can come again the next night, and the next.

I’m not sure who cancelled spring, but I’m not impressed. Yet again, the spring tides are accompanied by ear-numbing winds and a flurry of snow. Just the thought of plunging my hands into the pools makes my fingers ache, and yet, like the fool I am, I wade into the pools to see what’s there.

Due to my reluctance to leave my warm house, it’s half-past low tide by the time I hit the beach. The easterly winds are dashing the waves against the rocks and the gully I’d hoped to explore is well and truly submerged. All that’s left is an average-looking pool.

My average-looking pool for the 15 minute challenge

I’m tempted to give up and go home, but I’m always telling people that there’s something in every pool. That you just need to go slowly and look closely. I set myself a 15 minute challenge to find as many species as I can.

One of my first discoveries is this wonderful mutant cushion star. According to the books, these have five arms. Clearly this one hasn’t read the books. At some point it has lost one or more of its arms and in an incredible feat of regeneration it has sprouted an excess of new ones.

A Cushion star trying to pass as a Seven-arm starfish.

In fact, this cushion star has put so much energy into sprouting arms that it now has a total of seven arms. I do sometimes see another species, the Seven-armed starfish, but they are bright orange and have longer arms so I’m not fooled. It’s a nice try though.

There are lots of molluscs including several colourful painted topshells.

Painted topshell

Nearby, a colony of dog whelks huddles in a crack in the rock, around their yellow egg capsules.

A colony of dog whelks with their yellow egg capsules

It’s hard to see through the wind-rippled water into the tangled seaweed below, but this Calvadosia campanulata stalked jellyfish catches my eye. Its bright-white stinging cells stand out among the pink and red seaweed fronds.

Calvadosia cruxmelitensis stalked jellyfish

There are several more stalked jellies, including this Haliclystus octoradiatus. This species has a blob between each pair of arms, which acts as a sucker (‘primary tentacle’) allowing the jelly to flip upside down and cartwheel along the seaweed. This one seems to have two suckers between some of its arms. It also has an extra arm (nine arms instead of 8).

I start to wonder if this pool is going to be full of mutants with extra arms and tentacles.

The waves are breaking over the rocks and splashing over my back and the water level is rising precariously close to the top of my wellies. I take a few more quick photos of some wriggling worms, strawberry anemones and a banded chink shell just a few millimetres long.

Banded chink shell (Lacuna vincta)

As I leave the pool, I find a Saddle oyster shell. These small oysters attach to the underside of rocks and have round hole in the upper valve.

Cornish Rock Pools Junior loves Harry Potter. A while back he noticed that a lot of rock pool creatures have scientific names that sound like spells straight from a Hogwarts classroom.

Rock pool animals have many amazing (and disgusting) tricks up their sleeves. Some are simply fearsome looking like the Devil crab in the photo above. Others have weapons and disguises.

What better way to learn their names than by chanting them spell-style to unleash their freaky abilities?

So, wands at the ready – swish and flick – here are some top spooky rock pool spells.

Sepia officinalis – Invisibility spell

A cuttlefish shows off its camouflage skills in the IFREMER visitor centre, Concarneau, Brittany.

Nothing can hide better than a Common cuttlefish. Sepia officianalis can change colour and texture in an instant to make it invisible to both its predators and its prey.

Marthasterias glacialis – Regrow-an-arm spell

This Spiny starfish (Marthasterias glacialis) is regrowing two of its arms.

Many sea creatures like crabs and starfish can re-grow a lost limb. Starfish like this Spiny starfish can regenerate several arms at once, so it’s not uncommon to find one with just a couple of arms and three stumps.

Here’s a spooky story for you… Some say that fishermen in the North Sea used to hack starfish in half when they found them in their nets. Starfish attacked their catch so they were determined to get rid of them. They slaughtered all the starfish they could get their hands on, certain they were reducing the population. Instead, each half of the severed starfish began to regenerate, slowly regrowing its arms. So, every time the fishermen cut one in half, they created two starfish. Soon the area was swarming with starfish.

I’m not convinced this story’s true, but it makes a great Halloween tale!

Berthella plumula – Acid squirting spell

More dangerous than it looks – the Berthella plumula sea slug

Lots of sea slugs use poisons from their prey to defend themselves and some produce acid. The Berthella plumula can squirt out sulphuric acid from a special gland when it’s attacked. If you pick one up, it’ll make your skin blister and fall off (so best not to!).

Anemonia viridis – Harpoon stinging spell

The tentacles of the Snakelocks anemone are packed with harpoon-like stinging cells

Use this spell to unleash a secret weapon – the nematocysts. All jellyfish, anemones and other related animals have special stinging cells called nematocysts. Inside each cell is a coiled harpoon, which is fired out into anything that touches the tentacles.

Here’s a video of a pool full of Anemonia viridis eating an unfortunate fly.

Lineus longissimus – Smelly slime spell

A Bootlace worm on a rock – if you pick it up you’ll get stinky slime on your hands.

The bootlace worm is in the Guinness Book of Records as the world’s longest animal. When fully unravelled it often stretches 7 or 8 metres but the longest ever recorded was an incredible 55 metres long. More importantly, though, its special power is giving out a stinky slime. A perfect spell to use against your enemies!

Feeling worn out? Try the Elysia viridis spell instead of over-doing the trick-or-treat sweets. This amazing little sea slug retains energy-making chloroplasts from the seaweed it eats. The chloroplasts carry on making food for the slug through photosynthesis, giving the slug an ideal energy boost.

Aplysia punctata – Smoke screen spell

We must have accidentally disturbed a sea hare (Aplysia punctata), making it release a cloud of purple ink.

Sea hares (Aplysia punctata) may look like dull brown blobs, but they are as strange as rock pool creatures get. Not only do they lay eggs in the form of pink silly-string, but they have the ability to shoot out a cloud of purple ink when attacked, providing a perfect smoke screen.

These are just a few of the bizarre things our rock-pool creatures can do. There’s plenty more rock pool magic to learn.

If you’d like to know more about the gruesome habits of the animals on our shore, have a read of my guide to revolting rockpools. You can also take part in organised events to meet the creatures for yourself. Happy Halloween!

As you might imagine, we’re fans of nature documentaries in this house and we’re all looking forward to watching Steve Backshall’s new series, Fierce. It’s got me and Cornish Rockpools Junior thinking about opportunities to meet ‘fierce’ wild creatures closer to home.

Of course, these animals aren’t exactly fierce, they’re just equipped to survive the evolutionary arms race with attitudes, weapons and chemicals that aren’t very human-friendly.

You don’t need a plane, a film crew and a ton of equipment to seek out an encounter with a well-armed rockpool ninja. This weekend’s massive low tides are the perfect opportunity to head out onto the shore and check out our top 5 fierce(ish) rockpool creatures.

So, check the tide times, grab a bucket, put on your wellies and take a look…

5. Small spotted catshark

Scyliorhinus canicula – small spotted catshark, also known as dogfish – stranded in a Cornish rock pool

These small sharks, often known as dogfish, sometimes become stranded in pools during the very lowest of tides. They’re not at all aggressive, but it’ll sound impressive that you’ve met one. They have incredibly rough skin that used to be used as sandpaper. In some places you can also find their egg cases and those of their larger cousin, the nursehound, attached to seaweed. They take around 7-9 months to hatch out so never detach the egg case from the weed.

The developing greater spotted catshark can be seen at the bottom of this eggcase

4. Snakelocks anemone

This snakelocks anemone looks like it’s had a fright – the tentacles are being picked up by the current

This anemone is common in rockpools all around Cornwall. It’s easy to see how it gets its name from its long snake-like tentacles, which are usually green with purple tips, but sometimes a dull-brown. They’re from the same family as jellyfish and have stinging cells which shoot poisonous harpoons into anything that touches their tentacles. It’s best not to touch this anemone as some people have a reaction to the sting. If you do touch one be sure not to rub your eyes because stinging cells can attach to your skin – wash your hands as soon as you can.

Cornish Rock Pools Junior is convinced snakelocks anemones can eat your foot. That’s unlikely, but watch what they do to this fly…

3. Worms

Worms like this ragworm are often buried in sand and mud burrows – if disturbed they can shoot out their jaws and give a nasty nip.

An unlikely contender, but there are several species of worm on the shore that can be pretty fearsome, especially the larger ragworms. These animals have an extendible jaw that can shoot out and deliver a painful bite. Others, like the bootlace worm secrete a toxic mucus. Handle with care!

A bootlace worm. These worms are many metres long when fully extended, but are usually found in a tangled ball like this.

2. Compass jellyfish

Compass jellyfish – showing its distinctive markings

Like the anemone, this jellyfish is armed with lots of nematocysts (stinging cells), but far more powerful. These jellies with their distinctive V-shape compass markings can give you a painful sting. Jellyfish don’t live in the rockpools but are often washed in by the winds and tides, especially in the summer and autumn months. They’re beautiful creatures and well worth a look, but remember not to get close or to put your hands in the water – their tentacles can be hard to see, very long and can become detatched from the main jellyfish, so it’s not worth the risk (yes, that’s talking from experience… I’m a slow learner). There are lots of different species of jellyfish and some, including the massive barrel jellyfish, are harmless, but if you’re not sure, stay clear!

Jellyfish tentacles can be hard to see. It’s best not to put your hands in a pool that has a jellyfish in it (e.g. to take underwater photos of tentacles like this one!)

1. Devil crab (Velvet Swimming Crab)

A velvet swimming crab (devil crab) shows off its red eyes.

The top fierce creature award, as voted by Cornish Rock Pools Junior who will not go near them, is [insert fanfare of your choice here]… the velvet swimming crab. This crab, known by Junior and many others who’ve met it as the ‘devil crab’, is afraid of nothing and is always quick to use its pincers. Their dark shells and gleaming red eyes give these crabs a sinister look to match their temperament. They’re brilliantly suited to hunting in the rockpools and shallow seas. If you dare to look closely at one (see ‘How to pick up a crab’), you’ll see that their stripy back legs are flattened into paddles, making them excellent swimmers. Watch out for them lurking buried in the sand, with only those red eyes showing.

As soon as you approach a velvet swimming crab will stand on its back legs, its claws raised, ready for battle.

There are plenty more dangerous creatures, such as the weever fish and the Portuguese man o’ war, that didn’t make our list because we so rarely see them in the rock pools.

It almost goes without saying that by far the most dangerous creature on the shore is us humans. Marine litter, warming seas, pollutants, overfishing and habitat destruction all threaten our amazing marine life. Please do your bit every time you visit the shore:

If you turn any rocks replace them gently, the right way up.

Avoid using nets that can harm creatures and tread carefully.

If you catch any creatures, keep them in plenty of sea water and return them quickly to where you found them.

Don’t leave any litter behind and be aware that sun cream isn’t good for wildlife.

Every time you visit a beach take 2 minutes to pick up any rubbish you see.

Have fun and please do let me know what creatures you meet (fierce or otherwise) in the Cornish rock pools.

Have I mentioned that I don’t like the cold? Well I don’t, and worse than that I don’t function well in it; my fingers seize up, my brain goes fuzzy and my grumpiness level soars. Not ideal when I’ve agreed to meet up with a small army of children on a freezing, windswept beach. Fortunately I’m prepared and have no shame.

Junior’s still young enough not to notice or care about anything except whether I’ve brought his enormous metal spade. The other kids don’t seem worried either as I waddle over to them. They call me ‘the shark lady’. I think they mean that in a good way.

It’s amazing how fast children learn. A few minutes after he’s shown his first catshark egg case, a friend’s child is spotting them everywhere, his sharp eyes picking them out faster than me. We’ve soon clocked a couple of dozen of them. The parents find some too.

You might not think that rockpooling is the sort of activity that requires a warm up, but there’s nothing like practice for getting your ‘eye in’. The more and closer you look, the more you’ll see. What better excuse to get out on Cornwall’s beaches before, during and after this week’s massive tides?

I’ve been out on a few family rambles on the local shores the last couple of weeks to make sure I’m ready for some serious rockpooling this weekend (like most weeks, but they don’t complain).

If you’re wondering what you might see if you head down to the shore in the next few days, here are some of the things I’ve been finding…

Go slowly and look closely – this little ring of jelly contains thousands of eggs from a sea lemon (a type of slug).

It may seem too early in the year for rock pooling, but this is an exciting time of year on the shore. Spring has arrived in the Cornish rock pools and the huge clutch of eggs under the tail of a female green shore crab proves it.

Eggs come in all sorts of forms in the rock pools. Why not get out for your own ‘egg hunt’ on the shore this Easter?